1. Field of the Invention
The present invention relates to antifoamers having a good antifoaming effect on organic solvent systems which are being foamed.
2. Description of the Prior Art
Various types of antifoamers including silicone antifoamers have been used in industrial processes involving foaming. The silicone antifoamers such as oil compounds obtained by mixing silicone oils including dimethylpolysiloxane, methylphenylpolysiloxane, methylvinylpolysiloxane and the like with finely powdered silica. Emulsions of these oil compounds in water along with surface active agents have been widely utilized because they have better properties and, particularly, are chemically more stable than other types of antifoamers. They are also able to exhibit good effects in small amounts.
However, these silicone antifoamers exhibit good antifoaming effects on aqueous systems but have only very small effects on organic solvent systems in which the solubility of the silicone is high. For the antifoaming of organic solvent systems, there has been proposed a method using highly viscous dimethylpolysiloxane, for example, in Japanese Patent Publication No. 35-12564. This does not necessarily exhibit satisfactory antifoaming effects. Alternatively, there have been proposed antifoamers comprising perfluoroether compounds (Japanese Patent Application Laid-open Nos. 59-22611 and 60-22907) and antifoamers for organic solvent comprising perfluoroalkyl group-containing siloxanes (Japanese Patent Publication No. 35-12564 and U.S. Pat. No. 4,329,528). However, all of these antifoamers are not necessarily satisfactory with respect to the antifoaming effect.
Accordingly, there is a demand for the development of silicone antifoamers which have good effects on the antifoaming of organic solvent systems.